Process of preparing fibrous product from wood



May 21, 1946. I F. w. KRESSMAN I 2, 0 4

PROCESS OF PREPARING FIBROUS PRODUCT FROM WOOD v INVENTOR.

W), MATILORNEYZSL Q'Z W U WW May 21,1946. v F. w; KRESSMAN 2,400,546.

PROCESS OF PREPARING 'FIBROUS PRODUCT F-ROM WOOD Q INVENTOR.

QH r

zlzfgamwwq 3 MVM'ATTORNEYS.

Patented May 21, 1946 PROCESS PREPARING FIBROUS PRODUCT FROM -WOODFrederick W. Kressman, Laurel, Miss, assignor to Continental Turpentine& Rosin p! Inc.

Laurel, Miss, a corporation of Mississippi Application November 21,1942, Serial No. 466,523 4 ('Jlainis. I (O1. 202-39) This inventionrelates to a wood product and .process of preparing the same, and moreparticularly to a process of preparing highly absorbe'nt wood fibers ofsubstantially uniform density. 7 I

Onefeature of this invention is that wood may be reduced to a fibrousform with a'minimuin on tearing, breaking, or laceration of the fibers;another feature:-.Oi th'is invention is that a wood product of .s'u,ntially uniform absorbent quality is obtained. Still another feature ofthis in,- vention is th t anic liquids may be removed t appreciableweakening of the fibersi" acfurtherfeature of the invention is thetreatment ofthe wood particles or fibers with steam, which serves ,toremove the organic solvent and organic materials dissolved therein iron.the wood particles and at the same time serves more porous. In addition,many.small hard nonabsorbent particles result from the flbrationprocess. To obtain a satisfactory product, it-is necessary that thesevbe separated from the fibrous material.

I have found that wood, preferably inthe form of chips or other smallpieces, maybe fibrated to obtain an absorbent product. At this point,

to increase the moisture content of the wood,the'

increase in the moisture content of the wood being beneficial in thesubsequent steps in which the particles of wood are separated accordingto their densities.

Other features and advantages will be apparent from the specificationand the drawings. in which Fig. 1 is a plan view of an air classifier;Fig. 2

is a side elevational view; Fig. 3 is an end elevation; Fig. 4 is a sideelevational view, partly in section, all of the same device; and Fig. 5is a diagrammatic view showing broadly the steps.

of the process of the invention.

Ithas long been common in the artto treat Wood, such as yellow pine, toobtain-therefrom turpentine, rosin, and other organic products.

It has been the practice to take stumps of yellow I pine or othersuitable wood of little value, and reduce the material to small chips bya hogging or shredding operation. The chips are'steamed to removeturpentine and other volatile organic compounds, then extracted with anorganic solvent to obtain the rosin, and finally steamed again to removethe solvent. After these operations, the chips have no furtherusefulness and are discarded or'used for fuel.

I have found that these chips may be reduced to a fibrous jabsorbentform and in this state chamber.

the wood may be extracted with a suitable organic solvent, and thentreated with steam to remove the solvent. The non-absorbent particlesshould then be separatedfrom the resulting product, in order to obtain acommercially useful absorbent 'material.

' The process of fibrating the wood may be carried out in a Banburymixer, such as that described in PatentNo. 1,523,387, or other suitablemachine. Although the Banbury' machine was designed for and used in themixing of rubber, it is admirably adapted to this purpose.

' In operation, the pieces of wood are subjected to frictional contactwith two irregularly shaped members. which are rotated within the mixingFor convenience in loading, I prefer to add to the Banbury machine anadditional chamber of approximately thesame size as the mixing chamber.The additional chamber may be used as a reservoir, containing a completecharge ready for introduction into the mixing chamber.

' The rotating members in the mixing chamber subject the wood tofrictional, twisting, shearing, shredding contact with each other andwith the walls of the chamber. This action serves to reduce the wood tothe fibrous formwith a mini-.

. along the line of the grain of the wood.

become adapted to many uses. For instanceit.

maybe used as an absorbent material in roofing felt.

Even when the wood is properly reduced to" the fibrous form, extractionis desirable to Pro.- vide a maidmum absorbent-equality. Not only arethe organic liquids, which are removed, of

If desired, a lubricant may be used in the 'flbrating operation toreduce the laceration or breaking of the fibers in this step. Most oilsare suitable lubricants for this purpose, and a small quantity of oilmay be introduced into the mixing chamber withthe wood. Inthe case ofwood which contains large quantities of rosin, such as yellow pine forexample, the lubricant may, if desired, be eliminated since the largequantity of the rosin in the wood performs the lubricating function. Inthe Banbury machine, the frictional action develops a considerablevamount of heat, and the resulting temperature in the mixing chamber issuflicient to reduce the viscosity of the rosin and permit it to acteffectively as a lubricant.

great value,- but the resulting product is much If the temperature ofthe mixing chamber is Most of the disintegration is effected- Theproduct of the Banbury machine con- 5 sists of long thin fibers of woodwith smaller fibers extending therefrom, referred to herein as bundlesof fibers. Most of the disintegration takes place along the lines ofthe'grain of the wood.- As a result, the fibers are of relatively smalldimensions transverse to the grain. Such fibers are highly absorbent andporous, as compared to sawdust or other forms of wood reduced to smallparticles, such as the products of a grinding or attrition mill. Todistinguish from these and other methods of reducing wood to smallparticles, I refer to the process of reducing wood to fibrous form by aBanbury mixer or like machine as a wood fibrating process.

The ,former process for recovering organic liquids from the wood,to-wit: steaming. extrac- -tion, and then steaming, when applied to-thesuitable extraction apparatus may be used for this purpose. The variousorganic liquids removed from the wood may thereafter be separated byfractional distillation.- The or anic solvent may be removed from thefibers by subjecting them to steam, or, if it is not desirable toattempt to recover the solvent, merely'by a conventional dryingoperation.

The extracted fibrated-product is in a highly absorbent porous conditionand contains, after the steaming operation, ahigh percentage ofmoisture, usually about per cent. It may be 40 placed in a conventionaldryer and the moisture content reduced to approximately 15 per cent.

The step of separation of undesirable particles by means of an airclassifier maybe carried out highly fibrous and highlyabsorbentparticles than from the woody and less fibrous particles. Since thewoody and less fibrous particles are normally of a greater density thanthe more absorbent fibers, the drying operation tends to increase thedensity diii'erential between the particles. This isparticularlyimportant where only a portion of the moisture is removed by the dryingoperation. By referring to the moisture content to which the particlesare reduced. in the drying operation in V terms ,of percentage ofmoisture, the average moisture content of the particles is meant. Thehighly absorbent fibrous particles will, of course, contain a lowerpercentage of moisture than the woody, less fibrous particle's.

By treatingthe fibrated product with an airclassifier, substantially allof the non-absorbent particles may be removed. By the term fairclassifier is meant a device which, by passing the particles through arapidly flowing current of air, separates them accordingto theirdensities. A specific air classifier, for example, is disclosed herein fIn an air classifier of the structure which I prefer to use, a hopper i0is mounted above the head of a shaker table II. From a center line peakl2 the side I3 01 the table I! is inclined downwardly to the receptaclesN to 2i, inclusive, and the side 22 is inclined downwardly to similarreceptacles on the other side of the table. At the end of v the tableopposite the hopper ID, a V-shaped: guard 23 preventsmaterial frompassing over the end of the table. Guards 24 and 2-5, mounted adjacentthe hopper l0, serve the same purpose at the other end.

,The top surface of the table II supports a series of riilles or fins 26and 21 on either side of the peak. The riflles are higher at one andthan the other and are mounted in such a manner that the higher ends areadjacent to the guards 24 and 25. The lower ends approach the centerline of the table. Therefore. since the riilles 2] are in a positionsubstantially parallel to each other, they are graduated in length inorder that with material. having a moisture content as low none maycross the center line of the table.

as one per cent. On the other hand, the same step may be carried outwith material having a high moisture content,'although 35 per cent ormore of moisture is undesirable. However. for

- to the table I I by the member 30. Resilient sliding rocker arms 3|and 32 aid in controlling the most efiicient results, I prefer to reducethe moismotion.

ture only to between 12 per cent and 20 per cent.

not as a whole is unsatisfactory for commercial A fan 33 forcesa-rapidly, flowing current of air through the flexible duct 34 into thechamber use unless these particles are removed. The abrent of air evenlyalong the lower surface of the sorbent. qualities are not related to thesize of the particles, but are directly related to their density.

The steaming operation, by which the organic solvent together with theorganic materials distable.- The air then ,fiows through a series oftransverse apertures, such as the aperture 38, in

solved therein are removed from the wood fibers, a In operation, thefibrated extracted wood also serves to increase the moisture content ofthe fibers. Although the more absorbent and more I fibrous particlestend to absorb a greaterquantity of moisture, the steaming operation, inorder tobe effective for the'removal of the organic liquids, is normallysufficiently intensive to inabsorbedby the highly fibrous particles andthe less" fibrous :particles will usually be relativelyqo slight,particularly when a high percentage of moisture, 'such as 40% forexample, is incorporatedjinthefibrated product. The subsequent fjdryingoperation to which the fibersare subjected I removeSfla greater quantityof moisture from the 75, and pi lower absorbent quality. Thislatter-maof riflles 25 and 21 and permits them to pass down the sides i3and 22 of the table II to the receptacles on either side.- v I Theproduct collected in the receptacles to is, inclusive, is ofsubstantially uniform density and of'highabsorbentquality, while thatcollected in the receptacles 20 and 2l ,is, heavier coarse material, onthe other hand, passing oi! the end of the table, is discarded.

I have found that the highly absorbent material is also the most readilydried. Thus, when the fibrated extracted product leavesv the drier,

the non-absorbent particles will contain somewhat more moisture than thedesired product.

Since moisture increases the density of the prodnot, this aids in theseparation. Therefore, it

is preferable that the average moisture content of the particles be atleast per cent when the particles leave the drier.

The final product consists of a wood product in the form of long, thin,porous, highly absorbent fibers from which substantially all of theorganic substances, originally absorbed by the wood, have been removed.The bundles of fibers retain most of their original strength and areAlthough the invention has been described in connection with a specificembodiment, the foregoing detailed description is for the purpose ofillustration only. It will be understood, there fore, that changes andmodifications may be readily made in the process and product withoutdeparting from. the spirit and scope of the invention.

I claim:

l. A process of the character described for pre- Daring highly absorbentcellulose material from, -wood, comprising fibrating small pieces ofwood by subjecting them to a twisting, shearing, shredding, frictionalaction in a chamber to form fibrous particles of different absorbentqualities, the major portion of the particles being highly fibrous incharacter and other particles being woody and less fibrous and having agreater density than the highly fibrous particles, subject ing thefibrated product to extraction with a volatile organic solvent, steamingthe product to remove the organic solvent therefrom and to' increase themoisture content of the fibers. subjecting all of the particles tosubstantially uniform drying conditions for a sufllcient length of timeto remove a greater quantity of moisture from the highly fibrousparticles than from the less fibrous particles whereby an increase inthe 2,400, terial is again fed through the air classifier. The

stantially uniform drying conditions for a sum-" cient length of time toremove a greater quantity of moisture from the highly fibrous particlesthan from the less fibrous particles whereby an increase in the densitydifferential between the highly fibrous particles and the less fibrouswoody articles is effected, passing said fibers longitudinally over andalong a group of substantially parallel riflles, said riilles beinglongitudinally mounted on a transversely inclined platform, passing arapidly fiowing current of air from below said riflies through saidfibers, reciprocally and longitudinally agitating said platform, andcollecting the fibers of relatively low density.

3. A process of the character described for preparing highly absorbentcellulose material from wood, comprising fibrating the wood to formfibrous particles of different absorbent q alities, the major portion ofthe particles being highly fibrous in character and the other particlesbeing woody and less fibrous and having a greater density than thehighly fibrous particles, subiecting all of the fibrated particles toextraction with a volatile organic solvent, treating all of the fibratedparticles with'steam under substantially uniform conditions to removethe organic solvent therefrom and to introduce a relatively largepercentage of moisture into the product, subjecting all of the particlesto substantially uniform drying conditions for a sufilcient length oftime to remove a greater quantity of moisture from the highly fibrousparticles than from the less fibrous particles whereby an increase inthe density dif- 1 ferential between the highly fibrous particles andthe less fibrous woody particles is effected, and subjecting the mixtureof particles to air classi fication to separate the particles of lowdensity from the particles of high density. I

4. A process of the character described for pre paring highlyabsorbent'cellulose material from wood. comprising fibrating the wood toform fibrous particles of different absorbent qualities, the majorportion of the particles being highly fibrous in character and the otherparticles being woody and less fibrous and having a greater density thanthe highly fibrous particles, sub:

. jecting the particles to extraction with-a voladensity difierentialbetween the highly fibrous 2. A process of the character described forpre- I paring highly absorbent cellulose material from wood, comprisingfibrating small pieces of wood by subjecting them to a twisting.shearing, shredding, frictional action in a chamber to form fibrousparticles of different absorbent qualities,

the major portion of the particles being highly age moisture contentofthe particles to approximately fifteen per cent whereby an increase inthe density differential between the highly fibrous particles and theless fibrous woody particles is effected, and subjecting the mixture ofparticles t .air classification to separate the particles of low densityfrom the particles of high density.

, FREDERICK W. museum.

